I can't say for sure but it looks like it. Check out this thread where someone had a kindof similar issue.
https://www.linuxquestions.org/quest...he-4175456462/
Let me ask you this... when you enabled SSL for your gsm forum.. what all did you do? Because if you have ssl enabled already, then all you should need to use what I mentioned in step 1...
Code:
vBulletin 4
Go to Settings > Options > Site Name / URL / Contact Details.
Edit 'Forum URL' and add the 's' into the URL.
Example: https://www.vgchat.us
plus put this in the headers.
<meta http-equiv="Content-Security-Policy" content="upgrade-insecure-requests">
with the htaccess code as a optional failsafe incase that doesn't catch it all.